Extrusion die lubrication



Uttittd Sttttt Ptttttt This invention relates to improvements in theextrusion of metals and is concerned particularly with arrangements forlubricating a billet as it is forced through` an extrusion die. Byimprovements in lubrication, wear in the extrusion die is reduced andthe surface yfinish and dimensional control of the extruded productisimproved.

Particularly in the hot extrusion of largeV steel rods or v tubes,dificulty is experienced in providing' satisfactory lubrication ofextrusion dies and billets since, under the very high temperaturesinvolved in making the extrusion,

the lubricant tends to become veryfluid and leaches through the dieduring thefirst phase of extrusion. If the extrusion is a longone, mostof the lubricant is exhausted for the last part of the extrusion pass.Inadequate lubrication permits excessive wear in the extrusion die andconsequent `inferior finish of the surface of the article beingextruded.

` Many attempts have been made to improve this conditioncby utilizinglubricants of different characteristics, even going so far as using"glass asalubricant. But thus far, none of them seem to attain th'edesiredeffect.A This invention provides an arrangement for controlledlubrication of thebillet as`i't passes through the extrusion die, sothat a supply 1ofiappropriatelubricant,tplaced in the die cavity `beforethe extrusionbegins, `willtbe fed progres- `sively to the enteringregion of the` die and will last for tthe,l enti'reextrusion pass. u lObjects of the invention are extrusion" die and billet lubricationr andto provide a specific system to attain optimumlubrica'tion for anextrusion. The specific provisions of this invention are explained indetail inthe following specfctiqnfand are illustrated cin principleinthe attached`drawings, "ii1 which:

, Fig'. `l is ua longitudinal section `through portions of an fextrusionpress incorporating fthe" features of the invention,"

Fig. 2 is a section on the line 2-2 of Fig. 1, and

Fig. 3 is an enlarged detailed View of a portion of Fig. l, showing anextrusion in process.

In the drawings, the components of an extrusion press which are notgermane to the invention, are not shown, since general extrusion pressconstruction is well knownin the art. The particular parts of the presswhich are significant are shown, and include an extrusion die 10 whichis mounted in a die holder 12, the latter being removably mounted in adie carrier 14. The die carrier and consequently the holder and die aremovably mounted to engage the face of a billet container 16 which issecured in a container holder 18 forming part of the press. As is wellknown, the billet container usually comprises a hollow cylinder withinwhich a plunger 20 is slidably movable, the plunger comprising the endof a ram 22 which is usually driven by hydraulic means to press theplunger 20 rightwardly as shown into the billet container and toward thedie 10. lf tubular extrusions are to .be made, a mandrel 24 is securedto the face of the plunger 20, the mandrel entering the die aperture 26of the die 10 and irriprove the technique of i A passes through theaperture.

2,887,224 Patented May 19, 1959 ttt extriiding' abillet 28 placed in thedie container between the mandrel 24 and the die aperture 26.

The die aperture 26 establishes the external dimensions andcross-sectional form of the extrusion, and the billet 28 is ordinarilyforced into the aperture 26 along slopes or ramps 30 which form theentrance for the die 10. In the usual extrusion procedure, the interiorof the die con.- tainer and the inner face of Athe die 10 are generouslycoated with a suitable lubricant. Also, the billet 28 and the mandrel 24are generously lubricated. The kind of lubricant depends upon the speed,temperature, and pressure involved in the extrusion. Frequentlymaterials such as tallow, fortified with high melting point additivesare utilized. When steel extrusions are accomplished at temperatures ofthe order of 2200 F. and at high'pressure, the lubricant materialbecomes quite lluid and tends to leak through the die before muchprogress has been made in extruding the steel therethrough. Initialparts of the extrusion are adequately lubricated. However, if thelubricant, as is usual, is exhaustedv from within the billet containerbefore the extrusion is complete, the last part of the extrusion pass iscompleted withoutbenefit of lubrication which tends to increase therequired pressure for extrusion, to wear the die unduly, and todeteriorate the surface finish of the extrusion. It wouldbe desirable ifpossible to arrange for die lubrication throughout the entire extrusionpass to minimize die wear and to attain various other advantages. 1

According to my invention; I form the inner face of the extrusion diewith a groove or pocket 32, demarked from the face of the die by a land34. The pocket 32 and land `34`are annular in the arrangement shown, butneed not necessarily be annular.` The pocket 32 inconjunction withtheend of the bore of the billet container, forms a cavity of considerablecapacity which is filled with lubricant before a billet is loaded in thecontainer 16 and before the extrusion pass begins. This lubricant isindijcated at 36 in Fig.` 3. The lubricant pocket 32 iscon- 1nectedwiththe upstream end of the die aperture 26l by a plurality of conduits38 which are in the form of drillings,

so that lubricant in the pocket can flow to the die aperture,

,tliereby lubricating the aperture and thebillet immediately upstream ofthe critical point at which the extrusion is 45 j given its final sizingand its final finish.

`In the extruslon operation, the billet 28 is gradually necked downalong the ramps 30 until the billet material Initial lubricant containedon the die face and on the billet assists the material of the 50 `billetin passing over the ramps 30 and through the die 'aperture 26 butthismaterial as aforementioned, tends to exhaust itself before the extrusionis completed. The lubricant 36 in the pocket 32 on the die face providesa continuing supply to the critical portions adjacent the die aperture26 throughout the extrusion pass whereby the extrusion is given goodsurface finish and whereby die wear is reduced.

In` operation, when the extrusion pass starts, the billet is forcedfirmly against the land 34 on the die 10, sealing the lubricant in thepocket and allowing lubricant egressV from the pocket only through theconduits 38. As the extrusion pass continues, pressure builds up in thebillet container and the billet starts to flow through the die,substantially sealing off the downstream openings of the conduits 38 asthe billet mandrel passes through the die. This is the easiest flow pathfor the billet so that its wedging into the pocket 32 around the die rimdoes not take place rapidly. However, as pressure continues to beapplied, the billet material will gradually move into the pocket 32,forcing lubricant therefrom through the conduits 38 to ooze between thebillet and the die immediately upstream of the aperture 26, therebyproviding a 3 continuing source of lubrication for the billet as itextrudes through the die.

While the precise mechanics of the extrusion phenomenon are not known indetail, it is assumed that the die operates to a certain extent as aventuri. There is likely, a pressure differential existing whereby thepressure of the billet adjacent the pocket 32 is relatively high andstatic, whereas the pressure in the necked down part of the die adjacentthe aperture 26 is somewhat lower `due to the higher velocity of billetmaterial at this point. Thus, ypressurized lubricant from the pocketpasses through the conduits 38 to coat the billet immediately upstreamof the aperture 26. Furthermore, there is very slow movement of thebillet material adjacent the rim of the die and adjacent the boresurface of the billet container 16, whereas there is relatively highspeed of motion between the billet material and the die in the smalldiameter portion thereof adjacent the aperture 26. This relatively highspeed of motion enables the lubricant in the pocket to leach from thepocket to coat the billet material, under the influence of the staticpressure on the lubricant in the pocket 32.

After the plunger 20 has moved almost to the eX- treme right of thebillet container 16, the extrusion is substantially completed whereuponthe plunger 20 is withdrawn and the remaining part of the billet issecured from retraction by a groove 42 formed adjacent the right handend of the billet container. Thereafter, the die carrier 14 isdisengaged from the billet container holder 18, and moved away from it.The extrusion is backedup through the die a short distance, and theresidual part of the billet is cut off from the extruded product and isremoved from between the die carrier 14 and the container 16. Theextrusion is then drawn on through the die. Thereupon, the die carrier14 can be restored to the position shown in Fig. 1, and the extrusionpress is prepared for another extrusion pass by the appropriateapplication of lubricant as aforementioned,

making the system ready for the insertion of a new billet and thepressing of a new extrusion.

The lubricant pocket 32 for containing lubricant 36 is shown in thepresentyinvention as being annular and adapted for a certain form andshape of die 10, and the conduits 38 are symmetrically arranged aboutthe axis of the extrusion die which is shown as being adapted for theextrusion of circular tubes. For other extruded shapes and for diierentconfigurations of dies and presses,

the pocket for the lubricant 36 and the conduits 38 may be arranged inother manner than that shown to secure effective results. The pocket 32and conduits 38 are located to enable a suitable disposition oflubricant 36 between thedie and the extrusion to make the operation asecient as possible, The disposition of the features of the invention canbest be established experimentally to yield optimum 'results in reducingdie wear and in improving surface nish of the extrusion.

As shown at 38 in Fig. 3, the conduits may be disposed to deliverlubricant closer to the die aperture 26 than the conduits 38. Thecapacity of the pocket for the lubricant 36 may be made as large orsmall as required to contain suicient lubricant, so that an adequatesupply is assured throughout the entire extrusion pass. A principalrequirement lis that the pocket 32 be -located where it is exposed tohigh substantially static pressure; for convenience it may be located inthe die face as shown. It may be in the wall of the billet container, orin a separate compartment subject to the same or larger pressure thanthat to which the billet is exposed.

Though a single embodiment of the invention is shown, it is to beunderstood that the invention may be applied in various forms and invarious environments. Changes may ybe made in the arrangements shownwithout departing from the spirit of the invention. Reference should behad to the appended claim for denition'of the limits of the invention.

What is vclaimed is:

An extrusion apparatus including a container having a bore to receive abillet at one end for extrusion of the billet at the other end, a die inthe said other end having an extrusion orifice, the walls of saidorifice being of the cross-sectional shape of the extruded productdesired and sloping on a curve inwardly of said bore and radiallyoutwardly towards the wall of said bore and terminating in a planar facetransversely of said bore, said planar face adjacent the walls of saidbore being re'- cessed to forrn an annular pocket for lubricant, saidrecess opening into said bore whereby lubricantr contained therein willbe subjected to the direct pressure of the metal being extruded, andconduits extending from said recess to said curved surface forconducting lubricant under pressure thereto.

